The use of a MOS transistor as a power switch is known, for example, to block or restore a power supply current flow in an electric circuit. As an example, a MOS transistor may be used to control a lamp or a motor in series with the transistor, the assembly receiving a D.C. or A.C. power supply voltage. The MOS transistors used as power switches may be discrete components or integrated components (for example, in a semiconductor chip formed in CMOS technology).
A disadvantage of this type of switches is that a large semiconductor surface is necessary to be able to form a MOS transistor capable of withstanding high voltages and of conducting high currents.
Further, in the on state, MOS transistors have non-negligible leakage currents, thus causing an unwanted power loss.